Fire resistant construction members

ABSTRACT

Exemplary fire resistant construction members disclosed herein can comprise an engineered wood product I-joist and at least two panels comprising gypsum board secured to the I-joist. The member can comprise a first gypsum board panel secured to a first side of the member and a second gypsum board panel secured to a second, opposite side of the member. In some embodiments, gypsum board panels are secured to opposite sides of a web of the I-joist. In some embodiments, gypsum board panels are secured to opposite sides of upper and lower flanges of the I-joist.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/772,284, filed Mar. 4, 2013, which is incorporatedherein by reference.

FIELD

This application is related to fire resistant construction members.

BACKGROUND

Wood-based construction members can be vulnerable to fire damage. Forexample, some unfinished basement floor/ceiling assemblies areconstructed using wood-based load-bearing construction members, such asI-joists. When a fire occurs in a basement having an unfinishedfloor/ceiling assembly that includes such construction members, thefloor/ceiling assembly can be severely damaged by the fire and failprematurely. There is therefore a need for construction members havingimproved fire-resistance.

SUMMARY

Exemplary fire resistant construction members disclosed herein cancomprise a wood-based I-joist, such as comprising an engineered woodproduct, and at least two panels comprising gypsum board secured to theI-joist. The member can comprise a first gypsum board panel secured to afirst side of the member and a second gypsum board panel secured to asecond, opposite side of the member. In some embodiments, gypsum boardpanels are secured to opposite sides of a web of the I-joist. In someembodiments, gypsum board panels are secured to opposite sides of upperand lower flanges of the I-joist. Wood-based members other that I-joistscan also be protected with gypsum board panels to provide fireresistance.

In some embodiments, gypsum board panels are secured to opposite side ofthe web only, leaving the flanges exposed. The gypsum board panels canhave a height about equal to the height of the web. The thickness of thegypsum board panels can vary depending on the amount of fire-resistancerequired

In other embodiments, the gypsum board panels are secured to theflanges, such that each panel spans from an upper flange to a lowerflange, one on each side of the flanges. This can leave a hollow cavitybetween the gypsum board panels and the web. The height of the panelscan be about equal to the overall height of the I-joist, such that theflanges and the web are protected by the panels.

The gypsum board panels can be applied to an I-joist in the field using,for example, nails or screws. Some panels can be nailed or screweddirectly to the web, while other panels can be nailed or screweddirectly to the sides of the flanges. Some embodiments can comprise oneor more web holes passing transversely through the web and the gypsumboard panels, such as to allow for plumbing and wiring.

The foregoing and other features and advantages of the disclosure willbecome more apparent from the following detailed description, whichproceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a portion of an exemplary construction member.

FIG. 2 is a cross-sectional view of the construction member of FIG. 1taken along section line 2-2.

FIG. 3 is a side view of a portion of another exemplary constructionmember.

FIG. 4 is a cross-sectional view of the construction member of FIG. 3taken along section line 4-4.

DETAILED DESCRIPTION

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedisclosed methods, apparatuses, and systems should not be construed aslimiting in any way. Instead, the present disclosure is directed towardall novel and nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and sub-combinations withone another. The methods, apparatuses, and systems described are notlimited to any specific aspect or feature or combination thereof, nor dothe disclosed embodiments require that any one or more specificadvantages be present or problems be solved.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language. Forexample, operations described sequentially may in some cases berearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures and descriptions may not show thevarious ways in which the disclosed methods can be used in conjunctionwith other methods.

As used herein, the term “coupled” generally means physically coupled orlinked and does not exclude the presence of intermediate elementsbetween the coupled items absent specific contrary language.

Fire Resistance of Wood-Based Construction Members

Unprotected light-frame wood buildings do not have the natural fireresistance achieved with heavier wood members. Recently, language wasadded to the 2012 International Residential Code (IRC) requiring passivemembrane protection in an effort to increase the fire-resistance ofunprotected basement ceilings. Specifically, section R501.3 of the 2012IRC requires that floor assemblies include a 0.5″ gypsum wallboard (GWB)membrane, a 0.625″ wood structural panel (WSP) membrane, or equivalenton the underside of the floor framing member. Section R501.3, however,provides certain exceptions to this rule, including wood floorassemblies using dimension lumber or structural composite lumber (SCL)equal to or greater than 2″×10″ nominal dimension, or other approvedfloor assemblies demonstrating equivalent fire performance.

Within the membrane protection requirement, equivalence may be shown bycomparison to 0.5″ GWB or 0.625″ WSP. Equivalence may also be shown bycomparison to 2×10 assembly framing. Recent work by the American WoodCouncil (AWC) has sought to define the performance of a 2×10 assemblyand define the test method for making any kind of equivalencecomparison. The “AWC Policy and Guidelines on IRC Membrane ProtectionEquivalency” (October 2011) suggests that “to be considered equivalentto 2×10 sawn lumber or SCL, the framing members should support a loadcorresponding to 50% of the full bending design of the framing members,while being subjected to an ASTM E 119 time/temperature heating regime.All components utilized in the manufacture of the framing members(fasteners, plates, hardware, etc.) should be utilized during testing.The test end criteria should be structural member failure.” The AWCfurther suggests that “the most straightforward and accurate means ofdetermining the required minimum fire resistance time would be toestimate that time using the calculation methodology specified inNational Design Standard (NDS) Chapter 16 for unprotected solid-sawn2×10 floor joists assuming: a 3-sided exposure, a nominal char rate of1.5 inches/hour, a bending strength to allowable strength design (ASD)ratio of 2.85, and supporting a load corresponding to 50% of fullbending design.”

The calculation methodology specified in NDS Chapter 16 and the AWCassumptions above can be used to establish a fire-resistance benchmarkof approximately 15 minutes for 2×10 joist, as shown in Table 1 below.The result shown in Table 1 assumes a 3-sided exposure, nominal charequal to 1.5 inches per hour, strength to ASD ratio of 2.85, and 50% offull bending design.

TABLE 1 Calculated Fire-Resistance of 2 × 10 Joist Calculated Fire-Joist Size Resistance (min) 2 × 10 (1.5″ × 9.25″) 15.00

The calculation methodology specified in NDS Chapter 16 and the AWCassumptions above can also be used to estimate the fire resistance of anI-joist flange element, as shown in Table 2 below. The results shown inTable 2 assume a 4-sided exposure, nominal char equal to 1.5 inches perhour, strength to ASD ratio of 2.85, and 50% of full tension design.

TABLE 2 Calculated Fire-Resistance of I-Joist Flange Calculated Fire-Flange Size Resistance (min)  1.5″ × 2.5″ 13.14 1.125″ × 2.0″ 9.39

The calculation methodology specified in NDS Chapter 16 can also be usedto estimate the fire resistance of an I-joist web element, as shown inTable 3 below. The results shown in Table 3 assume a 2-sided exposure,nominal char equal to 1.5 inches per hour, and that the web iscompletely or nearly completely consumed at failure. At lower appliedloads, the web element primarily functions to maintain the distancebetween the tension flange and compression flange and to brace thecompression flange against bending failure.

TABLE 3 Calculated Fire-Resistance of I-Joist Web Web ThicknessCalculated Fire- (inches) Resistance (min) 0.375 3.71 0.500 5.29 0.6256.96 0.750 8.71 0.875 10.53 1.000 12.41

Improving Fire-Resistance of Wood-Based Construction Members

Disclosed herein are methods of increasing the fire resistance ofwood-based construction members, such as engineered wood constructionmembers (e.g., I-joists). These methods can involve application ofgypsum board to the wood-based members. The following examples can beused to provide equivalent fire-resistant performance per Exception 4 toSection R501.3 of the 2012 IRC (see above).

Gypsum Applied to Web

An exemplary construction member 10 is shown in FIGS. 1 and 2, in whichgypsum panels 20, 22 are applied directly to an I-joist web 12. Themember 10 comprises an upper flange 14, a lower flange 16, a web 12extending between the flanges, and gypsum panels 20, 22 applied toeither side of the web 12. The panels 20, 22 can comprise gypsum, gypsumwallboard, predecorated gypsum board, gypsum backing board, coreboard,and shaftliner board, water-resistant gypsum backing board, exteriorgypsum soffit board, gypsum sheathing board, gypsum base for veneerplaster, gypsum lath, gypsum ceiling board, and/or other gypsum-basedmaterials. The flanges 14, 16 can comprise a wood-based material, suchas structural composite lumber and/or solid-sawn lumber. In someembodiments, the web 12 can comprise oriented strand board (OSB) orstructural plywood.

The web 12 can have a thickness T1 of any size, such as from about 0.25″to about 1″, and a height H1 of any size, such as from about 9.5″ toabout 21″, or larger. The flanges 14, 16 can have a width W1 of anysize, such as at least about 1.5″, or at least about 3.5″, and can haveheights H2, H3, respectively, of any size, such as at least about1.125″, or at least about 1.5″. The panels 20, 22 can have thicknessesT2, T3, respectively, of any size, such as from at least about 0.25″ toabout 0.75″, or larger. In some embodiments, the panels 20, 22 cancomprise plural layers coupled together to form a single panel. Forexample, a 1″ thick panel can comprise two 0.5″ thick panels layeredtogether. The panels 20, 22 can have a height about equal to the heightH1 of the web 12, such that the panels 20, 22 substantially cover theentire height of the web 12 between the flanges 14 and 16 and/or providea snug-fit between the flanges.

The panels 20, 22 can be secured to the web 12 in any suitable manner,such as with fasteners, adhesives, positive locking mechanisms, frictionfits, other manners, or combinations thereof. In the illustratedexample, the panels 20, 22 are secured to the web 12 with fasteners 24and 26, which can comprise nails, screws, bolts, other fasteners, orcombinations thereof. For example, the fasteners 24, 26 can compriseType W drywall screws. The length of the fasteners 24, 26 can beselected based on the values of T1, T2, and T3. In the illustratedexample in FIGS. 1 and 2, each fastener 24, 26 extends through the panel20, the web 12, and into the other panel 22 in order to secure bothpanels to the web. In other embodiments, one or more of the fastenerscan be applied from the opposite side of the web 12, extending throughthe panel 22, the web 12, and into the panel 20. In one example,fasteners used to secure both panels to the web can have a length ofabout 1.375″. In some embodiments, the panel 20 can be secured to theweb 12 with a first set of fasteners applied through the panel 20 andinto the web, while the panel 22 can be secured to the web 12 with asecond set of fasteners applied through the panel 22 and into the web.In one example, fasteners used to secure only one of the panels 20, 22to the web can have a length of about F.

The construction member 10 can be constructed, such as in the field, bysecuring the gypsum panels 20, 22 to a wood-based I-joist. Because thegypsum panels 20, 22 primarily protect the web 12, the flanges 14, 16can remain exposed to fire damage. Thus, sufficiently sized flanges canbe provided in addition to the gypsum panels to provide the requiredlevel of overall fire resistance. Based on testing results, in order toprovide “equivalent fire-resistant performance” and/or in order tosurvive for the duration of the fire test described above, the flanges14, 16 can have a minimum width W1 of about 2.3″, about 2.5″, or about3.5″, and/or minimum heights H2, H3 of about 1.5″.

As shown in FIG. 1, the fasteners 24, 26 can be applied at intervalsalong the length of the member 10. FIG. 1 shows that, for example,fasteners 24A, 26A can be spaced an interval L1 from the fasteners 24B,26B, and fasteners 24C, 26C can be spaced a similar or differentinterval from the fasteners 24B, 26B. The interval L1 between fastenerscan be any size, such as from about 12″ o.c. to about 24″ o.c.

The fasteners 24, 26 can be positioned at various vertical locationsalong the height H1 of the web 12. For example, in the example of FIGS.1 and 2, the fasteners 24 can positioned a distance H4 below the upperflange 14, and the fasteners 26 can be positioned a distance H5 abovethe lower flange 16. H4 and H5 can be any size, such as about F.

As shown in FIG. 1, the member 10 can include a web hole 28 that passesthrough the web 12 and both panels 20, 22. The web hole 28 can allowtraverse access through the member 10, such as for plumbing and wiring.The web hole 28 can have a diameter of up to the height H1 of the web.The member 10 can have any number of such web holes along its length,and the web hole(s) can be located between the fasteners 24, 26 whenpresent. The impact of a web hole on the fire-resistance of the member10 can be minimal. The exposed web material around the perimeter of theweb hole 28 can char at its normal rate when the member 10 is exposed tofire and/or high temperatures. However, the charring of the web materialaround the perimeter of the web hole 28 may only make the hole slightlylarger between the panels 20, 22.

Table 4 below provides exemplary ratios relating how much raw material(gypsum board) is required on a per square foot basis of floor areausing the web-protected members 10 versus installing the membraneprotection currently required in the International Residential Code. Aratio greater than one indicates that it takes more gypsum boardmaterial to protect the web than to install a ceiling.

TABLE 4 Ratio of Gyp. Board Usage as Web Protection vs. Ceiling MembraneI-Joist O.C. I-Joist Depth Spacing 9½″ 11⅞″ 14″ 16″ 12″ o.c. 1.08 1.481.83 2.17 16″ o.c. 0.81 1.11 1.38 1.63 19.2″ o.c.  0.68 0.92 1.15 1.3524″ o.c. 0.54 0.74 0.92 1.08

Gypsum Applied to Flanges

Another exemplary construction member 40 is shown in FIGS. 3 and 4, inwhich gypsum panels 50, 52 are applied to the sides of the flanges 44,46 of an I-joist. The construction member 40 comprises an upper flange44, a lower flange 46, a web 42 extending between the flanges, andgypsum panels 50, 52 applied to either side of the web 42. The gypsumpanels 50, 52 can comprise gypsum, gypsum wallboard, predecorated gypsumboard, gypsum backing board, coreboard, and shaftliner board,water-resistant gypsum backing board, exterior gypsum soffit board,gypsum sheathing board, gypsum base for veneer plaster, gypsum lath,gypsum ceiling board, and/or other gypsum-based materials. The flanges44, 46 can comprise a wood-based material, such as structural compositelumber and/or solid-sawn lumber. In some embodiments, the web 42 cancomprise oriented strand board (OSB) or structural plywood.

The web 42 can have a thickness T4 of any size, such as from about 0.25″to about 1″, and a height H6 of any size, such as from about 9.5″ toabout 21″, or larger. The flanges 44, 46 can have a width W2 of anysize, such as at least about 1.5″, and can have heights H7, H8,respectively, of any size, such as at least about 1.125″. The gypsumpanels 50, 52 can have thicknesses T5, T6, respectively, of any size,such as from at least about 0.25″ to about 0.75″, or larger. In someembodiments, the panels 50, 52 can comprise plural layers coupledtogether to form a single panel. For example, a 1″ thick panel cancomprise two 0.5″ thick panels layered together. The panels 50, 52 canhave a height about equal to the sum of H6, H7, and H8, such that thepanels 50, 52 substantially cover the entire side surfaces of theflanges 44 and 46.

The gypsum panels 50, 52 can protect both the web 42 and the flanges 44,46 from fire and/or high temperatures. Because the flanges 44, 46 arenot exposed, as in the member 40 above, the size of the flanges is lesssignificant to the overall fire resistance of the member. Thus, a widervariety of sizes of I-joists can be used to construct the member 40while still providing sufficient fire resistance.

The construction member 40 can be constructed in the field by securingthe gypsum panels 50, 52 to a wood-based I-joist. The panels 50, 52 canbe secured to the flanges 44, 46 in any suitable manner, such as withfasteners, adhesives, positive locking mechanisms, other manners, orcombinations thereof. In the illustrated example, the panels 50, 52 aresecured to the flanges 44, 46 with fasteners 54, 55, 56 and 57, whichcan comprise nails, screws, bolts, other fasteners, or combinationsthereof. For example, the fasteners can comprise Type W drywall screwsor 5d cooler nails. The length of the fasteners can be selected based onthe values of T5, T6, and/or W2. In the illustrated example in FIGS. 3and 4, each fastener extends through one gypsum panel and into a flangein order to secure the panels to the flange. In one example, thefasteners used to secure 0.5″ thick gypsum panels to the flanges canhave a length of about 1.625″.

As shown in FIG. 3, the fasteners 54, 55, 56, and 57 (only fasteners 54and 56 are shown) can be applied at intervals along the length of themember 40. FIG. 3 shows that, for example, fasteners 54A, 56A can bespaced an interval L2 from the fasteners 54B, 56B, and fasteners 54C,56C can be spaced a similar or different interval from the fasteners54B, 56B. The interval L2 between fasteners can be any size, such asfrom about 12″ o.c. to about 24″ o.c.

The fasteners can be positioned at various vertical locations along theheights H7, H8 of the flanges 44, 46. For example, in the example ofFIGS. 3 and 4, the fasteners 54, 55 can positioned a distance H9 belowthe top of the upper flange 44, and the fasteners 56, 57 can bepositioned a distance H10 above the bottom of the lower flange 46. H9and H10 can be any size, such as about halve the values of H7 and H8,respectively, such as about 0.75″.

As shown in FIG. 3, the member 40 can include one or more web holes 58that pass through the web 42 and both panels 50, 52. The web holes 58can allow traverse access through the member 40, such as for plumbingand wiring. A web hole 58 can have a diameter of up to the height H6 ofthe web. The member 40 can have any number of such web holes along itslength, and the web holes can be located between the fasteners whenpresent. The impact of a web holes 58 on the fire-resistance of themember 40 can be minimal. Although a web hole provides access to thecavities between the panels 50, 52 and the web 42, flames and hot gassestend not to enter those cavities due to the lack of oxygen andventilation. The web material near the perimeter of the web hole 58 canchar due to flames entering the through the holes in the panels, but theflames and charring tend not to migrate further into the adjacentcavities. Furthermore, in some embodiments, the cavities between thepanels 50, 52 and the web 42 can include baffles and/or fill materialthat further reduces damage due to flames and/or heat entering throughthe web holes 58.

Table 5 below provides exemplary ratios relating how much raw material(gypsum board) is required on a per square foot basis of floor areausing the web and flange protected members 40 versus installing themembrane protection currently required in the International ResidentialCode. A ratio greater than one indicates that it takes more gypsum boardmaterial to protect the web and flanges than to install a ceilingmembrane.

TABLE 5 Ratio of Gyp. Board Usage as Web/Flange Protection vs. CeilingMembrane I-Joist O.C. I-Joist Depth Spacing 9½″ 11⅞″ 14″ 16″ 12″ o.c.1.58 1.98 2.33 2.67 16″ o.c. 1.19 1.48 1.75 2.00 19.2″ o.c.  0.99 1.241.46 1.67 24″ o.c. 0.79 0.99 1.17 1.33

Regarding the described gypsum protected members 10 and 40, the gypsumpanels can contribute in various ways that limit the growth of firedamage on the web and/or flange material. Some examples can include: 1)preventing surface burning of wood material, 2) reflecting/absorbingsignificant amounts of thermal and radiant energy, and 3) reducing theavailability of oxygen and ventilation.

In some embodiments, a member can comprise an increased web thickness,such as from about 0.5″ to about 0.0875″, in combination with gypsumpanels over the web and/or flanges, to provide increased fireresistance.

In view of the many possible embodiments to which the principles of thedisclosure may be applied, it should be recognized that the illustratedembodiments are only preferred examples and should not be taken aslimiting the scope of the disclosure. Rather, the scope of thedisclosure is defined by the following claims. We therefore claim allthat comes within the scope of these claims.

We claim:
 1. A fire resistant construction member comprising an internal portion comprising a wood-based material and an external portion comprising one or more gypsum panels.
 2. The member of claim 1, wherein the internal portion comprises an I-joist.
 3. The member of claim 2, wherein the external portion comprises one or more gypsum panels secured to a web of the I-joist.
 4. The member of claim 2, wherein the external portion comprises one or more gypsum panels secured to flanges of the I-joist.
 5. The member of claim 1, wherein the internal portion comprises a web portion comprised of oriented strand board or structural plywood.
 6. The member of claim 2, wherein the external portion comprises a first gypsum panel secured to a first side of the I-joist and a second gypsum panel secured to a second, opposite side of the I-joist.
 7. The member of claim 6, wherein the first gypsum panel is secured to a first side of a web of the I-joist, and the second gypsum panel is secured to a second, opposite side of the web.
 8. The member of claim 6, wherein the first gypsum panel is secured to a first side of an upper flange of the I-joist and to a first side of a lower flange of the I-joist, and the second gypsum panel is secured to a second, opposite side of the upper flange and to a second, opposite side of the lower flange.
 9. The member of claim 2, further comprising a web hole passing through the external portion and through a web of the I-joist.
 10. The member of claim 7, wherein the gypsum panels have a height about equal to a height of the web.
 11. The member of claim 8, wherein the gypsum members have a height about equal to a height of the I-joist.
 12. The member of claim 1, wherein the external portion is secured to the internal portion with mechanical fasteners.
 13. A construction member comprising an engineered wood product I-joist and at least one panel comprising gypsum secured to the I-joist.
 14. The member of claim 13, wherein the construction member comprises a first gypsum panel secured to a first side of the member and a second gypsum panel secured to a second, opposite side of the member.
 15. The member of claim 13, wherein the at least one panel is secured to one side of a web of the I-joist.
 16. The member of claim 13, wherein the at least one panel is secured to a lower flange of the I-joist and to an upper flange of the I-joist.
 17. The member of claim 13, wherein the at least one panel has a thickness of at least about 0.25″.
 18. A method of making a construction member, comprising: providing an I-joist comprising an engineered wood product, and securing at least one gypsum panel to a side of the I-joist.
 19. The method of claim 18, wherein securing at least one gypsum panel to a side of the I-joist comprises; securing a first gypsum panel to a first side of a web of the I-joist; and securing a second gypsum panel to a second, opposite side of the web.
 20. The method of claim 18, wherein securing at least one gypsum panel to a side of the I-joist comprises: securing a first gypsum panel to a first side of an upper flange of the I-joist and to a first side of a lower flange of the I-joist; and securing a second gypsum panel to a second, opposite side of the upper flange and to a second, opposite side of the lower flange. 